The invention relates to apparatus for the isotropic irradiation of the walls of cavities, especially spherical cavities, by means of a catheter containing a light conducting fiber and a deformable sleeve which is expandable by admission of a fluid.
Such apparatus are utilized for the illumination of the walls of cavities such as hollow organs. It is important that the light is uniformly distributed over the whole cavity walls.
Uniform distribution of the light radiation is a necessity, for example, in connection with internal photodynamic therapy, by means of laser light, of photosensitized tumors. A locally insufficient irradiation dosis does not completely destroy the tumor and leads to recurrences while excessive irradiation doses damage healthy wall areas. The tolerance range is generally only relatively small.
U.S. Pat. No. 4,612,938 discloses an apparatus which includes a light conducting glass fiber which is insertable into a spherical organ cavity such as a bladder in such a manner that its end is disposed centrally therein. For uniform scattering of the light the organ is filled with a dispersion liquid. A similar apparatus is described by D. Joeham et al. in "Porphyrin Localization and Treatment of Tumors", New York: Alan R. Liss, June 1984, pages 249 to 256.
In "Photochemistry and Photobiology" 46, No. 5, 1987, pages 619 to 624, W. M. Star et al. utilize for cavity irradiation a centrally arranged radiation emitter with spherical emission characteristics.
The first arrangement however requires high centering accuracy for the light emitting end of the glass fiber. Often such accurate positioning cannot be achieved particularly in situations in which the irradiation equipment is to be inserted into the hollow organ through a narrow catheter. In the second case the catheter itself generates shadows which result in insufficient irradiation of the organ wall areas near the axis of the catheter since the emitter is small relative to the diameter of the catheter.
It is the principal object of the present invention to provide an apparatus for the irradiation of cavity walls such as organs which provides for highly spherical emission characteristics especially with regard to the back portion of the cavity, that is, adjacent a catheter through which the radiation is introduced into the cavity and which is easily insertable through narrow openings in the organs or passages leading to the organ cavities.